麦套春棉主要害虫和天敌的生态位研究

调查了麦套着棉不同时期内,棉株上、中、下部棉蚜AphisgossypiiGover、棉叶螨TetranychustruncatusEhara、棉铃虫Helicoverpaarmigera（Hubner）和其主要天敌的数量。求得各期害虫与害虫、害虫与天敌、天敌与天敌之间的生态位宽度和重叠指数,并分析了它们彼此在空间上的竞争关系。     

杉木再生系统的比较研究

通过对杉木(Cunninghamia lanceolata Hook)再生系统的比较研究,建立了子叶、下胚轴、茎段和针叶等四个再生体系。子叶在附含1mg/L BA和0.1mg/L NAA的DCR培养基中再生频率为93.7%±0.45%,平均芽数为3.76±0.25;下胚轴在附含2mg/L BA和0.2mg/L NAA的DCR培养基中再生频率为96.2%±0.35%,平均芽数为17.4±0.18;茎段在附含1mg/L BA和0.1mg/L NAA的DCR培养基中再生频率达100%,平均芽数为3.28±0.11;针叶在附含1.5mg/L BA和0.1mg/L NAA的DCR培养基中再生频率达84.5%±0.45%,平均芽数仅为1.42±0.08。不定芽在附含0.2mg/L BA和0.02mg/L NAA的DCR培养基中有效伸长。芽苗经预处理后在附含0.3mg/L IBA的1/2 DCR培养基中生根效果最佳。     

Molecular organization in bacterial cell membranes III. Components of a “soluble” fraction obtained by n-butanol extraction of Streptomyces albus membranes

We have isolated a “soluble” fraction of Streptomyces albus G membranes or membranes previously solubilised by sodium dodecylsulphate, using n-butanol extraction. Polyacrylamide gel electrophoresis in sodium dodecylsulphate of the whole membrane showed a complex protein pattern (about 20–25 bands) with two predominant groups. The “soluble” fraction represented about 25% of the membrane protein and contained part of the major polypeptides. The yield of protein in “soluble” form decreased when membranes were suspended in water and di not significantly change if membranes were reduced with sodium dithionite and then treated with iodoacetamide. A change in relative mobility of some of these polypeptides seemed to occur with membrane delipidation. The proteins of the fraction appear to be glycoproteins as indicated by their simultaneous staining for protein and carbohydrate and the parallel sensitivity to trypsin of both stains. The apparent molecular weights by sodium dodecylsulphate gel electrophoresis of the proteins (glycoproteins) were: 63 000, 40 000 and 17 000. Similar protein patterns were obtained by extraction of the membranes with EDTA and non-ionic detergents. Lipid and nucleotide material were also found in the “soluble” fraction.The “soluble” fraction showed by gel filtration on Sephadex G-200 the existence of different states of aggregation. These states of aggregation revealed the same electrophoretic pattern of proteins, which seemingly corresponded to that of the original fraction (i.e. three protein groups with relative mobilities 0.65, 0.80 and 1.0). Treatment of the samples under different conditions with 1% dodecylsulphate (supplemented or not with 0.5% β-mercaptoethanol) failed to completely dissociate the fraction as shown by Sephadex filtration.     

Mutant p53 disrupts role of ShcA protein in balancing Smad protein-dependent and -independent signaling activity of transforming growth factor-β (TGF-β)

Biomarkers are lacking for identifying the switch of transforming growth factor-β (TGF-β) from tumor-suppressing to tumor-promoting. Mutated p53 (mp53) has been suggested to switch TGF-β to a tumor promoter. However, we found that mp53 does not always promote the oncogenic role of TGF-β. Here, we show that endogenous mp53 knockdown enhanced cell migration and phosphorylation of ERK in DU145 prostate cancer cells. Furthermore, ectopic expression of mp53 in p53-null PC-3 prostate cancer cells enhanced Smad-dependent signaling but inhibited TGF-β-induced cell migration by down-regulating activated ERK. Reactivation of ERK by the expression of its activator, MEK-1, restored TGF-β-induced cell migration. Because TGF-β is known to activate the MAPK/ERK pathway through direct phosphorylation of the adaptor protein ShcA and MAPK/ERK signaling is pivotal to tumor progression, we investigated whether ShcA contributed to mp53-induced ERK inhibition and the conversion of the role of TGF-β during carcinogenesis. We found that mp53 expression led to a decrease of phosphorylated p52ShcA/ERK levels and an increase of phosphorylated Smad levels in a panel of mp53-expressing cancer cell lines and in mammary glands and tumors from mp53 knock-in mice. By manipulating ShcA levels to regulate ERK and Smad signaling in human untransformed and cancer cell lines, we showed that the role of TGF-β in regulating anchorage-dependent and -independent growth and migration can be shifted between growth suppression and migration promotion. Thus, our results for the first time suggest that mp53 disrupts the role of ShcA in balancing the Smad-dependent and -independent signaling activity of TGF-β and that ShcA/ERK signaling is a major pathway regulating the tumor-promoting activity of TGF-β.     

高寒草甸生态系统牲畜种群结构和动态

本文用Leslie矩阵模型研究了高寒草甸生态系统牲畜种群结构及动态。模型考虑了更加精确的年龄组转移关系,出栏率是种群波动的主要因子。目前,牲畜种群结构不合理,种群数量不能保持平衡。     

Disruption of mitochondrial function during apoptosis is mediated by caspase cleavage of the p75 subunit of complex I of the electron transport chain

Mitochondrial outer membrane permeabilization and cytochrome c release promote caspase activation and execution of apoptosis through cleavage of specific caspase substrates in the cell. Among the first targets of activated caspases are the permeabilized mitochondria themselves, leading to disruption of electron transport, loss of mitochondrial transmembrane potential (DeltaPsim), decline in ATP levels, production of reactive oxygen species (ROS), and loss of mitochondrial structural integrity. Here, we identify NDUFS1, the 75 kDa subunit of respiratory complex I, as a critical caspase substrate in the mitochondria. Cells expressing a noncleavable mutant of p75 sustain DeltaPsim and ATP levels during apoptosis, and ROS production in response to apoptotic stimuli is dampened. While cytochrome c release and DNA fragmentation are unaffected by the noncleavable p75 mutant, mitochondrial morphology of dying cells is maintained, and loss of plasma membrane integrity is delayed. Therefore, caspase cleavage of NDUFS1 is required for several mitochondrial changes associated with apoptosis.     

Structural consequences of metallothionein dimerization: solution structure of the isolated Cd4-alpha-domain and comparison with the holoprotein dimer

The NMR determination of the structure of Cd(7)-metallothionein was done previously using a relatively large protein concentration that favors dimer formation. The reactivity of the protein is also affected under this condition. To examine the influence of protein concentration on metallothionein conformation, the isolated Cd(4)-alpha-domain was prepared from rabbit metallothionein-2 (MT 2), and its three-dimensional structure was determined by heteronuclear, (1)H-(111)Cd, and homonuclear, (1)H-(1)H NMR, correlation experiments. The three-dimensional structure was refined using distance and angle constraints derived from these two-dimensional NMR data sets and a distance geometry/simulated annealing protocol. The backbone superposition of the alpha-domain from rabbit holoprotein Cd(7)-MT 2 and the isolated rabbit Cd(4)-alpha was measured at a RMSD of 2.0 A. Nevertheless, the conformations of the two Cd-thiolate clusters were distinctly different at two of the cadmium centers. In addition, solvent access to the sulfhydryl ligands of the isolated Cd(4)-alpha cluster was 130% larger due to this small change in cluster geometry. To probe whether these differences were an artifact of the structure calculation, the Cd(4)-alpha-domain structure in rabbit Cd(7)-MT 2 was redetermined, using the previously defined set of NOEs and the present calculation protocol. All calculations employed the same ionic radius for Cd(2+) and same cadmium-thiolate bond distance. The newly calculated structure matched the original with an RMSD of 1.24 A. It is hypothesized that differences in the two alpha-domain structures result from a perturbation of the holoprotein structure because of head-to-tail dimerization under the conditions of the NMR experiments.     

分离自冬虫夏草可培养真菌的多样性研究

冬虫夏草是生长于青藏高原的一种名贵中药材。天然冬虫夏草及其微环境中生活着多种真菌。作者使用常规分离培养方法对冬虫夏草的真菌区系进行研究。从天然冬虫夏草的子座、菌核和菌膜3个部位共分离到572个真菌菌株,并根据形态特征将大部分菌株鉴定到37个不同的属。这些菌株经SSCP(single-strand conformation polymorphism)分析后,再根据nrDNAITS序列的相似性(以97%为阈值)共区分出92种不同的分类单元(operational taxonomic unit,OTU)。其中,属于子囊菌的菌株数及OTU数均比接合菌和担子菌多。从菌膜分离的菌株数及OTU数都明显多于子座和菌核。分离自子座的优势真菌是产黄青霉Penicillium chrysogenum,而分离自菌核和菌膜的优势真菌均为玫红假裸囊菌Pseudogymnoascus roseus。尚未最终鉴定的部分真菌可能为新的真菌物种。     

MicroRNAs and their role in viral infection

Recently, a class of about 22 nucleotides (nt) small RNA has been discovered in many eukaryotes, termed microRNAs (miRNAs), which have a variety of functions. Many recent findings have demonstrated that viruses can also encode their own miRNAs. Meanwhile, other findings reveal a relationship between host miRNA and viral infection. These findings suggest a tight relationship between host and viral infection via miRNA pathway. This article introduces the miRNAs encoded by viruses and reviews the advances of the interaction of the mammalian host miRNAs and viral infection.